In VX2 tumor model of Japanese white rabitts, fundamental investigation on the antitumor effects of microwave irradiation with w/o/w poly-hematoporphyrin ether/ester (PHE) emulsion were carried out.The intratumoral concentration of PHE at 6 hours after local injection of w/o/w PHE emulsion (in volving PHE 0.5mg/kg) was 10.4<plus-minus>2.4mug/g, and it was almost equal to the concentration after intravenous administration of PHE (2mg/kg). On the other hand, serum concentration of PHE after local injection of w/o/w PHE emulsion was under limit of measuremenThe reduction ratio of the tumor by microwave irradiation after administration of PHE was observed 89.8<plus-minus>12.1% in local injection of w/o/w PHE emulsion and 77.4<plus-minus>20.7% in intravenous administration of PHE,respectively without hyperthermic effect caused by microwave itself. Antitumor effect was not recognized in microwave irradiation alIn conclusion, local injection of w/o/w PHE emulsion may be beneficial as an administration route of PHE and microwave irradiation after PHE administration has possibility for a new treatment of superficial malignant tumors.